Abstract
BackgroundThe role of Fusobacterium nucleatum Fap2 protein in the development of colorectal cancer has recently been explained. Fap2, when bound to the human inhibitory receptor, TIGIT, inhibits the cytotoxic activity of natural killer (NK) cells against cancer cells, thus, allowing proliferation of the latter eventually leading to tumor growth. The aim of the study was to identify the immunogenicity of a peptide mimotope of the Fap2 protein and to determine the reactivity of colorectal cancer patients’ sera against the mimotope.MethodsImmunogenic epitope of the Fap2 protein of F. nucleatum was selected using the B-cell epitope prediction of the Immune Epitope Database and Analysis Resource (IEDB). The immunogenicity of the synthetic peptide mimotope of the Fap2 protein was determined in animal models and reactivity of colorectal cancer patients’ sera against the mimotope was done by indirect ELISA.ResultsResults show that the selected peptide mimotope, with sequence TELAYKHYFGT, of the outer membrane protein Fap2 of F. nucleatum is immunogenic. Increase in the absorbance readings of peptide-immunized rabbit sera was observed starting Week 1 which was sustained up to Week 10 in the indirect ELISA performed. Colorectal cancer cases (n = 37) were all reactive in an ELISA-based analysis using the mimotope as the capture antigen.ConclusionsIn this study, we identified an immunogenic epitope of the Fap2 protein of the Fusobacterium nucleatum. We demonstrated the reactivity of serum of histopathologically confirmed CRC patients in a peptide-capture indirect ELISA which may serve as proof of concept for the development of CRC diagnostics.
Highlights
The role of Fusobacterium nucleatum Fap2 protein in the development of colorectal cancer has recently been explained
The sequence of the predicted immunogenic epitope was TELAYKHYFGT which is located at the 3596th to 3606th position of the Fap2 protein
The synthetic peptide mimotope of the selected immunogenic epitope was reported to be soluble in ultrapure water, 0.1 M phosphate buffered saline (PBS) pH 7.1, and DMSO, at a gross peptide concentration of less than 15 mg/mL
Summary
The role of Fusobacterium nucleatum Fap protein in the development of colorectal cancer has recently been explained. Fap, when bound to the human inhibitory receptor, TIGIT, inhibits the cytotoxic activity of natural killer (NK) cells against cancer cells, allowing proliferation of the latter eventually leading to tumor growth. The aim of the study was to identify the immunogenicity of a peptide mimotope of the Fap protein and to determine the reactivity of colorectal cancer patients’ sera against the mimotope. The composition of the gut microbiome has recently been implicated in the development of colorectal cancer (CRC) [1]. The association of F. nucleatum with CRC development is attributed to the ability of patients’ infected cancer cells to inhibit the ability of the immune system to attack tumoral cells [7, 8]
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